Ultrahigh-frequency measuring apparatus



March 30, 1954 D. PACKARD 2,673,963

ULTRAHIGH-FREQUENCY MEASURING APPARATUS Filed Nov. 5, 1951 2Sheets-Sheet l mam/Erf March 30, 1954 PACKARD 2,673,963

ULTRAHIGH-FREQUENCY MEASURING APPARATUS Filed NOV. 5. 1951 2Sheets-Sheet 2 l INVENTOR. aW/o ,Dac/ard Patented Mar. 30, 1954ULTRAHIGH-FREQUENCY MEAsURiNo APPARATUS David Packard, Los Altolett-Packard Compan poration of California s, Calif., assignorto Hewy,Palo Alto, Calif., a cor- Appucatian November 5, 1.951,- serizu N0.254,945

(ci. 33e-9s) 2 claims.

This invention relates generally to ultrahigh frequency electricalmeasuring apparatus and more particularly to apparatus known in the artas standing wave detectors.

Standing wave detectors customarily employ a high frequency transmissionline provided with a slotted outer conductor. A probe or like pickupdevice is adapted to extend into the slot and is Supported by a suitablecarriage, whereby it is movable lengthwise v Suitable electronicequipment is connected to the probe to enable making standing wave andimpedance measurements. The outer slotted conductor of the transmissionline may be the outer tubular conductor of a coaxial line,or the tubularwall of a wave guide. A characteristic of prior equipment of thischaracter is that the outer con'- ductor is integrally or permanentlyattached to means which serves to support and track the carriage. Agiven piece constructed to operate with a transmission line of certainelectrical characteristics. This limits the range of usefulness of theapparatus, whereby many separate pieces of equipment are required rangeof frequencies.

It is an object ofthe present invention to providev siznplied apparatusof the above character which will make possible application to a widefrequency range.

Another object of the invention is to provide a 'A applied or exchanged,to ,-t

o f the transmission line. io

of equipment is therefore ilu in which' the preferred embodiment hasbeen set Q forth in' detail in conjunction with the accompanyingdrawing.

Referring to the drawing:

Figure l isa planview illustrating apparatus incorporated in the presentinvention.

Figure 2Y isa side elevational`- view of the ap paratus shown in Figure1.

Figure Sis an end view of the apparatus.

Figure' 4 is a cross-sectionalr view taken along the line 4-4v of Figure1.

The apparatus illustrated in the drawing consists generally of acarriage I0 adapted tdfhave rectilinear movement in opposite directions,and which serves to detachably mount a suitable pickup device or probeIl.

The tracking means for 55 the carriage is secured to the members l2,which form means for detachably mounting the transmission line sectionI3 in cooperative relation with the probe and carriage.

In the specific construction illustrated, the carriage consists of abody part le that provided with the central opening 5 for removablyaccommodating the probe Il. The probe is removably retained by suitablemeans such as the set screw il. The carriage is tracked upon theparallel guide rods i8 and lll, which have their ends secured to themembers l2. In order to provide tracking to a high degree of accuracyand a minimum amount of friction, it is desirable to provideballebearing bushings Ztl of the linear type which are fitted within theforward and rear portions 2l and 22 of the carriage, and which embraceand slide along the rods i8 and le.

The mounting members l2 are formed U- s'haped, or in other words theyare in the form of inverted saddles. The legs or side branches d20. ofthe-se members are shown provided with leveling screws 23, to facilitatesupporting' the apparatus in' a desired horizontal position.

The means illustrated for manually moving the carriage includes a shaftwhich is journaled to the carriage, and to which the knob sand pinion.536 are attached. The pinion engages a gear rack 2l, which is formed onthe rod 28V. Rod together with a similar rod 2S at the rear side of theapparatus, extend between and are secured at their extremities to themembers l2.

The ultrahigh frequency wave guide section I3 illustrated in Figure lhas its one side wall provided with longitudinal s'lot 3 l. In theparticular construction illustrated theV body of the wave guide isformed of two halves 32, which are duplicates, and' which are machinedto form the longitudinal slot 3l. The two halves are ac'- curatelysecured together as by means of the lower meeting flanges 33 and the endcoupling flangesY 3ft. The flanges provide means for making connectionwith other portions or sectionsof a complete transmission system.

The means provided for accurately locating waveguide section l3 withrespect to the carrie ge is asfollows: The upper face 3e of the wave g"Le section accurately machine-fl to form a true planar surface.Laterally extending lugs or ears 3? are provided near the ends of thesection', and are provided with threaded openings 3S. The cross bars 52hof the mounting members l2 have downwardly faced pads 39, and the lowerfaces 4I of these pads are accurately machined to be in a common planeand to meet with the upper surfaces of the ears 31. Screws 42 areloosely accommodated in the members l2, and are adapted to be threadedinto the openings 38, whereby the wave guide can be rmly clamped againstthe pads 39. This form of attaching means provides for highly accuratelocation of the wave guide section with respect to the carriage and theprobe, and in addition it enables a particular guide to be readilyremoved, and another guide of different size applied.

In making highly accurate measurements it is desirable to use varioustypes of indicating means to indicate the position of the carriage. Thusa calibrated strip 43 is attached to the members I2, and extends inproximity with the carriage. The carriage has a Vernier calibrated strip44 which is located in proximity with the strip 43. As additionalindicating means, I can employ a dial indicator 45 of the micrometertype, which can be mcvably secured to the supporting post 45 on thecarriage. The operating member 4l' of the dial indicator can abut a zeroadjustment screw 48, which is carried by the stationary support post 49.By the use of such a dial indicator it is possible to indicate theposition of the carriage to a high degree of accuracy.

Operation of the apparatus described above is as follows: Depending uponthe frequency range desired, a wave guide or coaxial section is attachedto the mounting members l2, with its coupling slot 3l in cooperativerelation with the probe il. The ends of the wave guide or transmissionline section are then connected to additional sections of a completesystem. The probe i i is connected to suitable electronic indicating ormeasuring equipment by suitable means such as a flexible cable. Byvirtue of the accurate positioning of the wave guide section, the pickuploop of the probe is accurately located within the slot 3 i, and ismaintained in accurate alignment with the slot as the carriage and theprobe are moved to diiferent operating positions. By providing aplurality of transmission line sections of different sizes andelectrical characteristics, the apparatus can be adapted to a wideoverall range. Each such section is constructed with machined attachinglugs corresponding to the lugs 31, and the distance between centers ofthe tapped openings is the same for each section, whereby all of thesections can be replaceably mounted upon the members l2. For a frequencyrange of say from 10 to i000 megacycles, two sections can be provided ofthe coaxial type, with the outer conductor being slotted and constructedto provide mounting means in the manner described above.

For frequencies ranging from say 2600 to 13,000 megacycles, transmissionline sections of the wave guide type can be employed with the mountingmeans of cach section being the same.

It will be evident from the foregoing that the invention greatly extendsthe useful range of application of standing wave detectors. Theapparatas has a high degree of accuracy for a selected frequency band,and the same degree of accuracy can be maintained for selected frequencybands over a wide range. A minimum amount of time is required foradapting the apparatus to different selected frequency bands, and aminimum amount of equipment is required to take measurements over a widefrequency range. Be-

cause of the novel construction ofthe mounting means, includingparticularly the saddle-like members I2, it is possible in manyinstances to apply the apparatus to a transmission line section whichhas previously been connected in a transmission system, without thenecessity of first removing a section, before the apparatus is applied.In other words, it is possible to place the apparatus over a wave guidesection and engage the screws 42 to effect accurate positioning betweenthe carriage and the wave guide section, without disconnecting the endsof the wave guide section from adjacent sections.

I claim:

1. In ultrahigh frequency electrical apparatus for standing wavemeasurements, a carriage, a detector probe secured to the carriage, apair of inverted U-shaped mounting members, each mounting member havingdepending side branches and an upper` horizontal bar portion connectingthe side branches, the side branches forming laterally spaced legs forsupporting the apparatus, means connecting said mounting members fortracking the carriage whereby the carriage can be moved in oppositedirections between the mounting members, downwardly faced pads formed onthe lower sides of said connecting bars, the lower faces of the padsbeing in a common plane, a transmission line section positioned withinsaid mounting members and including an outer slotted conductor, mountingears formed on the outer conductor of the section and proportioned tomeet said pads, with accurate location of the slotted conductor relativeto the carriage, and releasable means for clamping the section againstsaid pads.

2. In high frequency electrical apparatus for standing wavemeasurements, a carriage, a detector probe secured to the carriage, apair of inverted U-shaped mounting members, each mounting member havingspaced depending side branches, and an upper horizontal bar portionconnecting the side branches, the branches forming spaced vertical legsfor supporting the apparatus, means connecting the said mounting membersfor accurately tracking the carriage whereby the carriage can betraversed in opposite directions between the mounting members,downwardly faced pads formed on the lower sides of said connecting bars,the lower faces of said pads being in a common plane, a transmissionline section capable of being transposed through the spacing betweensaid legs to a position within said mounting members, said sectionincluding an outer conductor having a longitudinal probe accommodatingslot in that side of the conductor that is faced toward the carriage,spaced upwardly faced mounting ears formed on said conductor and locatedgenerally on opposite sides oi the slot therein, said ears beingproportioned to meet said pads with accurate location of said linesection relative to the carriage end probe, and releasable means forclamping said ears against said pads.

DAVID PACKARD.

References Cited in the file of this patent UNITED STATES PATENTS Number

